Enlarge / Is it natural, or is it us? (It’s us.) (credit: Andriy Onufriyenko/Getty Images)
It starts as a reasonable question: If the Earth’s climate changed before humans existed, how can we be so sure the current change is due to us and not something natural?
To answer that question, we need to understand what caused the natural changes of the past. Fortunately, science has a good handle on the causes of Earth’s natural climate changes going back hundreds of millions of years. Some were cyclical; others were gradual shifts or abrupt events, but none explain our changing climate today.
A zombie claim
With energy policy and elections in the news, the claim by some politicians that climate change is natural is once again bubbling up from the disinformation swamp. So I asked some scientists a very unscientific question: What would they buy if they had a dollar for every time they heard it?
